This invention relates generally to determining position by electromagnetic radiation. More particularly, the invention relates to an improved system for using sensed position data to maintain a desired distribution of machines.
As the world becomes a more crowded and busy place, there are an increasing number of machines, on land, on sea and in the air. The machines perform a variety of functions and many are man driven vehicles. Many of the machines are groups of like machines which are traveling through space. For example, fleets of oil tankers may voyage from port to port on the sea. Floating weather detection buoys or individual bomblets within a cluster bomb are other examples. As the group of machines moves, it would be desirable to manage the distribution of these machines so that they maintain a desired distribution with respect to each other. The desired distribution of machines may be for a variety of purposes such as collision avoidance, maintaining a minimum separation for sampling purposes or distributing death onto thine enemy. The desired distribution need not be uniform across the cluster as certain areas may require greater service or attention.
The Global Positioning System (GPS) is currently the most precise positioning system generally available to the general public and has significantly dropped in price in recent years. The GPS comprises a network of 24 satellites orbiting the earth. Each satellite transmits a ranging signal modulated on a 1.575 Ghz carrier. By monitoring the signal from a plurality of satellites, a GPS receiver can determine its position, i.e. latitude, longitude and altitude, to an accuracy of about 100 meters. In general, this degree of accuracy would be attained if signals from three or four of the GPS satellites were received. More accurate GPS signals are available to the military. Differential GPS, also available to the public, is more accurate than standard GPS, but requires an additional land based transmitter and special permission from the government.
Many of the uses for GPS-based systems known to the Applicants are in the realm of mapping or collision avoidance applications. Notably one such GPS-based system is taught by "Traffic Alert and Collision Avoidance Coding System", U.S. Pat. No. 5,636,123 to Rich et al. In the Rich system, the airspace is divided up into a grid of volume elements. A collision avoidance signal is transmitted wherein the carrier signal is modulated by a psuedonoise code which is function of the volume element in which the aircraft is located. Each aircraft only tracks collision avoidance signals from vehicles in its own and immediate surrounding cells. Based on the calculated paths of the aircraft, a warning of an impending collision can be provided to the pilot.
The Applicants have proposed an improved tracking and collision avoidance system in "Time Multiplexed Global Positioning System Cell Location Beam System" Ser. No. 09/239,335 filed the same day as the present application, is commonly assigned and is hereby incorporated by reference. Although the invention described in the incorporated application does not address the problems of maintaining the distribution of machines as they move throughout their environment, it does share an overall cell structure with the preferred embodiment of the present invention.
This invention solves these and other important problems.